Large Gap Two-Dimensional Topological Insulators with the Significant Rashba Effect in Ethynyl and Methyl Functionalized PbSn Monolayers

Abstract

Two-dimensional (2D) topological insulators (TIs) have recently attracted a great deal of attention due to their nondissipation electron transmission, stable performance, and easy device integration. However, a primary obstacle to influencing 2D TIs is the small bandgap, which limits their room-temperature applications. Here, we adopted first-principles to predict inversion-asymmetric group IV monolayers, PbSn(C 2 H) 2 and PbSn(CH 3 ) 2 , to be quantum spin Hall (QSH) insulators with large topological gaps of 0.586 and 0.481 eV, respectively. The nontrivial band topologies, which can survive in a wide range of strain, are characterized by topological invariants Z 2 , gapless edge states, and the Berry curvature. Another intriguing characteristic is the significant Rashba SOC effect which can also be tuned by feasible compressive and tensile strains. Meanwhile, the hexagonal boron nitride (h-BN) provides a suitable substrate for growth of these films without influencing their topological phases. These novel materials are expected to accelerate the development of advanced quantum devices.

Evidence of Topological Phase Transition with Excellent Catalytic Activity in the AgCaAs Heusler Alloy: A First-Principles Investigation

“…The evolution of electronic band structure (with and without SOC) under strain (from 0 to 6%) is given in Figure S2 of the Supporting Information. This characteristic is quite similar to the previously reported work . A band inversion occurs at 6% in the presence of SOC (see Figure c).…”

“…This characteristic is quite similar to the previously reported work. 66 A band inversion occurs at 6% in the presence of SOC (see Figure 5c). Therefore, a 26.2 meV non-trivial energy gap arises as a result of the topological phase transition from normal insulator to TI.…”

Large gap two-dimensional topological insulators with the coexistence of a significant Rashba effect and piezoelectricity in functionalized PbGe monolayers

“…In addition, the elastic constants of PbGe(CN) 2 and PbGe (C 2 H) 2 were calculated to inspect their mechanical stability. By using the Voigt notation, considering that they are 2D materials and have P3m1 point-group symmetry, their elastic tensor can be expressed by the following formula: In practical application, we can select the appropriate substrate materials with large band gaps, such as h-BN 30,31 and SiC, 32 for the growth of PbGe(CN)2/PbGe(C 2 H)2 monolayers.…”

“…According to the Born criteria of mechanical stability for 2D materials ( C 11 > 0 & C 11 > C 12 ), both PbGe(CN) 2 and PbGe(C 2 H) 2 are mechanically stable. In practical application, we can select the appropriate substrate materials with large band gaps, such as h-BN 30,31 and SiC, 32 for the growth of PbGe(CN)2/PbGe(C 2 H)2 monolayers.…”

Insights into selected 2D piezo Rashba semiconductors for self-powered flexible piezo spintronics: material to contact properties

“…The large dipole moment of 0.50 debye introduces RSS (α R = 0.85 eV Å) in g-TlAs monolayer. Functionalized PbSn monolayers were researched by Wang et al [64] and the α R s are obtained as 2.24 and 3.92 eV Å in PbSn(C 2 H) 2 and PbSn(CH 3 ) 2 monolayers respectively. Ariapour and Babaee Touski [65] explored the group-III monochalcogenide MX (M = Ga, In and X = S, Se, Te) monolayers.…”